Low power and Lossy Networks (LLNs), e.g., sensor networks, have a myriad of applications, such as Smart Grid and Smart Cities. Various challenges are presented with LLNs, such as lossy links, low bandwidth, battery operation, low memory and/or processing capability, etc. A primary challenge for LLNs is to make effective use of the limited and dynamic network capacity.
Existing and widely deployed approaches to Quality of Service (QoS) and Call Admission Control (CAC) typically used in “classic” IP networks are for the most part ill-suited for LLNs. Heavy signaling can easily overwhelm the limited network capacity and strict resource reservation mechanisms cannot operate effectively when there are not enough resources to allocate (limited memory). In current IP networks, there are two paradigms used to meet SLAs (Service Level Agreement) in networks carrying flows with different characteristics and QoS requirements: 1) Use of QoS: edge traffic marking (IPv6 DS byte), queuing disciplines, Random Early Detection/Discard, etc.; and 2) CAC using signaling (e.g., RSVP) in the network to perform explicit bandwidth reservation.
What QoS provides is the ability to prioritize critical traffic but this implies potential large packet buffering, which may be problematic on nodes with very limited resources. CAC using a protocol such as RSVP allows for explicit bandwidth reservation between the source and destination, however such explicit CAC requires potentially heavy state maintenance.